Adrenergic mechanisms in multiple sclerosis: the neuro–immune connection?

Paradoxical effect of cortistatin treatment and its deficiency on experimental autoimmune encephalomyelitis

Cortistatin is a cyclic-neuropeptide produced by brain cortex and immune cells that shows potent anti-inflammatory activity. In this article, we investigated the effect of cortistatin in two models of experimental autoimmune encephalomyelitis (EAE) that mirror chronic and relapsing-remitting multiple sclerosis. A short-term systemic treatment with cortistatin reduced clinical severity and incidence of EAE, the appearance of inflammatory infiltrates in spinal cord, and the subsequent demyelination and axonal damage. This effect was associated with a reduction of the two deleterious components of the disease, namely, the autoimmune and inflammatory response. Cortistatin decreased the presence/activation of encephalitogenic Th1 and Th17 cells in periphery and nervous system, and downregulated various inflammatory mediators, whereas it increased the number of regulatory T cells with suppressive effects on the encephalitogenic response. Moreover, cortistatin regulated glial activity and favored an active program of neuroprotection/regeneration. We further used cortistatin-deficient mice to investigate the role of endogenous cortistatin in the control of immune responses. Surprisingly, cortistatin-deficient mice were partially resistant to EAE and other inflammatory disorders, despite showing competent inflammatory/autoreactive responses. This unexpected phenotype was associated with elevated circulating glucocorticoids and an anxiety-like behavior. Our findings provide a powerful rationale for the assessment of the efficacy of cortistatin as a novel multimodal therapeutic approach to treat multiple sclerosis and identify cortistatin as a key endogenous component of neuroimmune system.

Changes in autonomic modulation to the heart and intracellular catecholamines. A longitudinal study in differentiated thyroid carcinoma during short-term hypothyroidism and thyroid hormone replacement

BACKGROUND

The effects of thyroid deprivation on the autonomic modulation to the heart remain controversial.

METHODS

In this study in patients followed for thyroid carcinoma, we investigated (1) heart rate variability parameters and the baroreflex gain and (2) intracellular catecholamine levels in circulating lymphocytes during short-term hypothyroidism (phase 1) and after reinstitution of TSH-suppressive thyroid hormone replacement (phase 2).

RESULTS

The RR interval value (p < 0.01) and systolic blood pressure (p < 0.05) were higher in phase 1 than in phase 2. The low-frequency/high-frequency (LF/HF) ratio was significantly lower in the hypothyroid state (p < 0.05), with a higher HF component (p < 0.05). After adjusting for mean RR interval in the regression model, the difference between the power of RR interval oscillations calculated in the two states was greater for the LF band (p = 0.005) and it was borderline significant for the HF band (p = 0.052). The baroreflex gain alpha(LF) index was similar in the two phases. The stimulus-induced cellular production of norepinephrine and epinephrine in peripheral blood mononuclear cells was significantly higher in phase 2.

CONCLUSION

The neurally-mediated influences on the sinus node and the study of intracellular catecholamine production suggest a reduced sympathoexcitation in hypothyroidism compared with the treatment phase. The early increase in blood pressure observed after thyroid hormone withdrawal is not due to impaired sensitivity of the baroreflex arc.